There are many different incontinence disposable child and adult care products on the market including diapers, training under pants, and temporary swimsuits. Many of these products are constructed with nonwoven substrates including but not limited to nonwoven polyethylene or nonwoven polypropylene films. There is a desire within the marketplace to print graphics on these nonwoven substrates for appearance such as mere decoration or for utility such as indication of wetness. These substrates are typically printed with flexographic or rotogravure presses for these products, however, the printed inks have low color transfer resistance so as to discolor anything the nonwoven substrate may come into contact with such as clothing, carpet and furniture. The nonwoven substrate is not porous such as paper and thus the printed ink easily transfers from the substrate onto contact substrates/objects. Thus, there is a desire for the printed graphics on nonwoven substrates to have augmented color transfer resistance properties.
Various inks have been used to print on non-woven substrates over the years, with limited success due to the substrate. A non-woven substrate is nonporous and thus the printed ink can easily transfer from the non-woven substrate onto contacted substrates or objects. Conventional printed inks have low color transfer resistance and thus have a tendency to discolor anything the non-woven substrate may come into contact with, such as clothing, carpet and furniture.
U.S. Pat. No. 5,458,590 describes printing solvent based block urethane inks on non-woven substrates. The block urethane ink system is composed of a block urethane resin, vinyl resin, wax and epoxidized soybean oil along with pigments and is not acceptable for human garment contact due to the specific block urethane used. U.S. Pat. No. 5,695,855 discloses adhesive inks used on non-woven products. U.S. Pat. No. 5,853,859 describes the combination of a latex polymer and pigment along with a cure promoter for improving colorfastness when exposed to liquids having a pH of 2-13. International Publication Number WO 02/051644 A1 discloses a cross linked ink with a cross-linked coating for use on nonwoven substrates.
However, the prior art technologies for printing on non-woven substrates are generally characterized by being dependent on the particular printing process or fail to exhibit the superior color transfer resistance properties needed for printings on the non-woven substrate in applications where they are subjected to abrasion. Non-woven substrates are typically used for many different incontinence disposable personal care products which include diapers, training under pants and temporary swimsuits where they are subjected to excessive rub and abrasion. There is an unmet need in the marketplace for printing inks suitable for printing graphics on non-woven substrates for appearance such as mere decoration, or for functional utility such as wetness indication, where the printed graphics have superior color transfer resistance properties. In addition, none of the prior art technologies employ water based ink technology for printing nonwoven substrates. Solvent based printing inks contain high levels of volatile organic compounds (VOC's), which limit their use to printers who are either permitted to release VOC's to the atmosphere or have solvent incineration equipment installed. For many printers, these limitations require them to use water based printing inks.
These needs and many others are met by a printing ink used on non-woven substrates comprised of a water based polyurethane resin, water, and colorant. Other advantages of the present composition will become apparent from the following description.